This tutorial has been written solely in Arabic, ofcourse, not on WordPress or I would have commited suicide, I hope this helps you more get to taste the sweet flavour of networks, I’m done with you ignoring my other network articles (mad)

The OSI Reference Model:
The early development of networks was chaotic in many ways. The early 1980s saw tremendous increases in the number and sizes of networks. As companies realized that they could save money and gain productivity by using networking technology, they added networks and expanded existing networks as rapidly as new network technologies and products were introduced.

By the mid 1980s, companies began to experience difficulties from all of the expansions they had made. It became more difficult for networks using different specifications and implementations to communicate with one another. The companies realized that they needed to move away from proprietary networking systems—those systems that are privately developed, owned and controlled. In a computer industry, “proprietary” is the opposite of “open“.

Proprietary means that one company or a small group of companies controls all use of the technology. Open means that use of the technology is available free to the public.

Bus topology: in a bus topology a cable proceeds from one computer to the next. The main cable segment must end with a terminator to absorb the signal when it reaches the end of the line or wire. If there is no terminator, the electrical signal representing the data bounces back at the end of the wire, causing errors in the network.

Star and Extended-Star topologies: the Star topology is the most common physical topology in Ethernet LANs. It is made up of a central connection point that is a device, such as a hub, switch, or router, where all the cabling segments actually meet. Each device on the network is connected to the central device with its own cable.

Although a physical star topology costs more to implement than the physical bus topology, the advantages of a star topology make it worth the additional cost. Each device is connected to the central device with its own wire, so that if that cable has a problem, only that one device is affected, and the rest of the network remains operational. This benefit is extremely important and is the reason why almost every newly designed Ethernet LAN has a physical star topology.

When a star network is expanded to include an additional network device that is connected to the main network devices, the topology is referred to as an extended-star topology. The problem with the pure extended-star topology is that if the central node point fails, large portions of the network can become isolated.

Ring and Dual-Ring topologies: unlike the physical bus topology, a ring type of topology has no beginning or end that needs to be terminated. Data is transmitted in a way that is very different from the logical bus topology. In one implementation, a “token” travels around the ring, stopping at each device. If a device wants to transmit data, it adds that data and the destination address to the token. The token then continues around the ring until it finds the destination device, which takes the data out of the token. The advantage of using this type of method is that there are no collisions of data packets, later I will explain what collisions in a network are.

In a single ring topology, all the devices on the network share a single cable, and the data travels in one direction only. Each device waits its turn to send data over the network. The single ring, however, is susceptible to a single failure, stopping the entire ring from functioning.

In a dual ring topology, two rings allow data to be sent in both directions. This setup creates redundancy (fault tolerance), meaning that if one ring fails, data can be transmitted on the other ring.

Mesh and Partial-Mesh topologies: another type of topologies that is similar to the bus topology is mesh topology (لو كانت مش طبولوجي تبقى ايه :P). The mesh topology connects all devices to one another for redundancy and fault tolerance. Implementing a full mesh topology is expensive and difficult. This method is the most resistant to failures, because any single link failing will not affect reach ability, why? You will understand that when I explain switching and interconnections.

In a partial-mesh topology, at least one device maintains multiple connections to all other devices, without being fully meshed. This method reduces the cost of meshing all devices by allowing the network designer to choose which nodes are the most critical and appropriately interconnect them.

Sorry guys but I have decided not to publish anything in Arabic unless it was some small text with no extensive formatting required, I have noticed that the look of my blog went buggy on both IE and FF not to mention that any edit to any arabic post will lead into aftermath disasters.

Thus I declare the Keylogger topic is suspended until revised again.

If you need a shoulder now I know just the right guy for that, Nour, go get him 😛

Security researchers Erik Tews and Martin Beck have succeeded in partially cracking the WPA (Wi-Fi Protected Access) encryption, which until now had been considered safe. The two hackers will demonstrate their feat at the upcoming PacSec security conference in Tokyo, Japan.

WPA is a protocol that has been widely adopted as a replacement for WEP (Wired Equivalent Privacy), which has been known to be insecure since as far back as 2001. The initial attack on WEP was actually a dictionary attack, thus requiring great computational resources. This meant that attack scenarios on a large scale were highly unlikely.
The uncertainty ended at the beginning of 2007, when Erik Tews, along with two student colleagues from the Darmstadt University of Technology in Germany, developed a new technique which allowed them to break WEP security in only two minutes. Their method, which became known as the PTW attack, prompted all security professionals to declare WEP a high security risk. In fact, the use of WEP as encryption protocol is what allowed hackers to steal millions of credit card details in the T.J. Maxx hit.